Problem: Solve for $x$ : $x^2 - 16x + 64 = 0$
Answer: The coefficient on the $x$ term is $-16$ and the constant term is $64$ , so we need to find two numbers that add up to $-16$ and multiply to $64$ The number $-8$ used twice satisfies both conditions: $ {-8} + {-8} = {-16} $ $ {-8} \times {-8} = {64} $ So $(x {-8})^2 = 0$ $x - 8 = 0$ Thus, $x = 8$ is the solution.